THE  DEVELOPMENT  OF  A YELLOW 
GLAZE  FOR  TERRA  COTTA 


DONALD  BURGESS  ATWELL 


THESIS 

FOR  THE 

DEGREE  OF  BACHELOR  OF  SCIENCE 

IN 

CERAMIC  ENGINEERING 


COLLEGE  OF  ENGINEERING 
UNIVERSITY  OF  ILLINOIS 


1922 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/detaiis/deveiopmentofyeiOOatwe 


/a  So  as.  LAP 


/ 9sa 
Ai  3 


UNIVERSITY  OF  ILLINOIS 

i9i22. 

THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

Donald B u r g e s s Atwell 

ENTITLED 


IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF P.? Science 


HEAD  OF  DEPARTMENT  OF 


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TABLE  OF  COITTEBTR 
Part  One 

Page 

I.  Introduction  1 

II.  Biscuseion  of  Previous  Work  and  Literature  3 

III.  Exo ^=ri mental  Method  Emnloyed  6 

IV.  Body,  Slins  and  Glazes  Investigated  7 

V.  Blending,  Dimoing  and  Firing  11 

VI.  Results  13 

Table  No.  1,  Results  14 

VII.  Conclusions  15 

Part  Two 

I.  Changes  in  Glaze  Comoo  sit  ion  l6 

II.  Preoaration,  Blending,  Aopli  cation,  Firing  17 

III.  Results  18 

Table  No.  2 19 

Table  No.  3 20 

Graoh  Firing  Schedule  21 

IV.  Summary  22 

V.  Conclusions  23 


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The  Development  of  a Yellow  Glaze  for  Terra  Cotta 

Part  One 
I 

I nt roducti  on 

In  develoning  a yellow  glaze  for  terra  cotta  there  are  three 
things  to  con  sider. 

A glaze  for  such  use  must  mature  well  at  the  cone  to  which 
terra  cotta  ware  is  burned,  which  is  usually  about  Sager  cone 
five  (5’)»  It  must  develop  the  desired  gloss  and  be  free  from 
erazing,  pinholing,  feathering  and  all  glaze  ■'defects  at  this 
cone , 

The  glaze  to  be  useful  as  a terra  cotta  glaze,  must  be 
such  that  it  mil  mature  properly,  without  defects,  when  applied 
on  a green  terra  cotta  body  over  a slip  which  has  been  previous- 
ly applied.  A terra  cotta  cla;^^  mix  does  not  burn  to  a v/hite,  and 
because  of  this  it  is  necessary  to  use  a white  opague  slip  be- 
tween the  glaze  and  the  body  so  that  the  color  of  the  body  will 
have  no  effect  on  the  glaze  colors. 

The  use  of  the  coloring  oxide  is  very  important.  The  col- 
oring oxide  should  be  such  that  it  will  nro  :^ce  good  yellows 
which  are  clear  and  of  such  a strength  that  a aeries  of  shades 
may  be  obtained  by  variations  in  the  amount  of  the  coloring  oxide 
used.  The  coloring  strength  of  the  oxide  has  a bearing  on  the 
nracti cabi li ty  of  its  use  commerci ally,  for  if  excessive  amounts 
have  to  be  used  to  nroduce  the  desired  denth  of  color  in  the 
glaze  it  may  not  be  economically  practical  to  use  it  as  a pig- 
ment substance. 

Summarizing,  my  objectsrof  research  are: 


2 

1.  To  develoT)  a glaze  which,  was  suitable  for  use  at  Cone 
fi  ve  (5)  together  with  a slip  on  a green  body. 

2.  To  secure  a combination  of  glaze  and  coloring  oxide 

to  produce  a yellov;  which  would  be  satisfactory  from  the  color 
standpoint  and  be  economically  suitable  for  use  as  a glaze  for 
terra  cotta  ware. 


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II 

Discussion  of  Previous  ’^Vork  and  Literature. 

There  seems  to  he  pretty  close  agreement  as  to  the  yellow- 
producing  oxides  and  pigment  materials  in  the  various  authorit- 
ative hooks  on  the  subject  of  glazes  and  ceramic  colors.  The 
range  of  materials  for  the  production  of  yellow  colors  in  glazes, 
as  obtained  from  the  various  sources  includes  uranium  oxide, 
iron  oxide,  antimony  oxide,  titanic  oxide,  leukonin,  (sodium 
antimonate)  tungstic  acid,  molyhdi  c oxide,  and  a coloring  fritt 
made  uo  of  uranic  nitrate  fritted  with  feldspar.  The  various 
references  and  subject  matter  from  them  are  as  follows: 

1.  R.  Fainbach-  "Pottery  Decorating". 

According  to  -^-.ainbach,  very  handsome  nure  yellows  are  ob- 
tained by  the  use  of  antimonic  oxide  in  a white  glaze  in  the 
nronorti  ons  of  five  to  ten  per  cent  (5-10.^^)  oxide  and  ninety 
to  ninety-five  ner  cent  (90“9?^)  glaze.  Ke  also  states  that 
ferric  oxide  and  uranium  oxide  develop  yellows,  the  ferric 
oxide  also  being  used  v.dth  antimony  oxide  for  procuring  reddish 
or  brovmi sh  red  yellows.  He  is  also  the  authority  for  the  state- 
ment that  very  handsome  yellows  have  been  obtained  with  silver, 
but  this,  obviously,  is  too  expensive  a material  for  use  as  a 
coloring  oxide  in  a terra  cotta  glaze. 

2.  A.  B.  Searle-  " Ceramics  Industries  Pocket  Book". 

In  his  list  of'colors  used  in  pottery,  glazing,  enamelling 
and  glass-staining",  Searle  lists  the  oxides  of  titanium, 
antimony,  iron  and  uranium  as  being  yellow-nro ducing  oxides. 


4 


3.  Emile  Bourry-  ’’Treatise  on  Ceramics  Industries”. 

Bourry  states  that  the  oxide  of  uranium  gives  a yellow  in  an 
oxidizing  fire.  Ke  also  states  that  titanic  acid  develops  yellows. 
To  use  his  words;  ”In  glazes  it  (titanic  acid)  gives  only  yellow 
tints,  due,  partljr  at  least,  to  the  iron  that  raw  titanic  acid 
always  contains  in  commerce.*  He  is  authority  for  the  statement 
that  pure  iron  oxide  develops  a good  jrellow, although  it  tends 
toward  a brown  at  high  teraperatxires.  He  lists  uranium  oxide  as  a 
good  yellow-producing  oxide,  except  in  the  presence  of  lead,  where 
it  turns  to  an  orange, 

4.  Taxile  Doat-  "Grand  Feu  Ceramics”. 

the  authority  for  the  use  of  nitrate  of  uranium  fritted  with 
feldspar  as  producing  yellows  is  found  here.  Doat  also  advocates 
the  use  of  uranium  oxide  for  3?”0llows,  as  well  as  oxide  of  iron  for 
slightly  brownish  yellows. 

5.  Chemical  Abstracts,  AX,  93;  ii'ew  Yellow  Color''-  Vnon. 

According  to  this  article,  aerium  phosphates  have  been  used 
to  develop  birilliant  yellows. 

6.  Notes  on  Ceramics  3. 

I found  in  my  Ceramics  notes  a statement  as  to  the  use  of 
tungstic  acid*  and  molybdio  oxide  in.  the  presence  of  manganese  for 
the  development  of  yellow  glazes. 

7.  Report  of  German  Cera-iiic  cociety,  Dr.FurJ:. 

Reference  was  made  in  this  report  to  the  use  of  cerium  oxide 
for  the  development  of  yellow  glazes,  no  authority  being  given  for 
the  statement. 

♦.  Hertwig,  Sprechsaal,  49 i 1845-1846  (1903),  Abstract  in  the 


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yellow  and  orange  shades  with  the  use  of  tungstic  acid. 

8.  Kertwig-Sprechsaal  49;  p.l20. 

Cerium  phosphate  is  used  for  the  development  of  hrilliant 
yello’"s,  according  to  this  authority. 

9.,  Hermann  A.  Ce  ger,  Collected  Writings. 

Seger  uses  titanic  acid  in  the  development  of  hrilliant 
yellows  in  underglaze  colors  at  lov/  temperatures.  Ke  makes  the 
statement  that  the  yellow  color  may  he  due  to  the  presence  of 
iron  as  an  impurity. 

Uranium  is  also  used  hy  f^.ger  for  the  development  of  lemon 
yellows.  With  the  use  of  uranium  the  necessity  of  avoiding 
reducing  conditions  becomes  naramount. 

1 0.  Frank  H,  Riddle,  "The  Coloring  Power  of  Uranium  Oxide  in 
Glazes  of  Various  Comnositi  ons.  T . A..  C.  S. , Vol.  8. 

The  statement  is  made  that  the  coloring  power  of  urani’jm 
oxide  is  very  great,  as  little  as  .006  equivalents  producing 
a decided  yellow. 

11.  Farl  T.  Montgomery-  "Study  of  Underglaze  Colors  with  View 

of  Determing  the  Most  Insoluble  and  Hon-Volat ile  Underglaze  Color 
Comoosition.  T . A. C. S.  Vol.  13» 

Montgomery  finds  that  yellov;i  sh  grays,  yellomsh  blacks  and 
yellovdsh  greens  are  develoned  mth  uranium  oxide.  The  color 
was  lorepared  as  a fritt.  The  higher  members  gave  the  colors  noted 
above.  There  i s no  reference  in  this  to  there  being  any  reducing 
conditions  in  the  burn. 


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III 

Experimental  Method  Employed. 

The  method  of  procedure  in  the  work  consisted  of  the 
following  steps; 

(a)  Selection  of  a hody  material  "which  would  closely  ap- 
proximate the  hody  actually  used  in  commercial  hody  as  t o gen- 
eral behaviour. 

(h)  Selection  of  a suitable  white  slip  for  use  in  masking 
the  color  of  the  hody,  being  used  for  application  on  the  green 
hody. 

(c)  Selection  of  a glaze  suitable  for  ap"olication  over  the 
white  sli"0  on  the  green  body. 

( d)  Consi  deration  and  investigation  of  the  coloring  oxides 
which  are  thought  to  be,  and  have  been  reported  to  be  yellow- 
producing  oxides,  together  with  a consideration  of  the  proper 
"oroportions  necessary  for  incorporation  v/i  th  the  glaze  to  produce 
satisfactory  shades  of  yellows. 


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7 

IV 

Body,  Sli-ps  and  Glazes  Investigated. 

1.  Body.  The  body  used  was  made  of  Bloomingdale  Stoneware  clay. 
Preparation  of  the  body  consisted  of  grinding  in  a v/et  pan  and 
forming  briguettes  about  three -fourths  of  an  inch  thick  and  two 
inches  wide  by  four  inches  long.  These  were  formed  in  a small 
brick  auger  machine  by  the  use  of  a suitable  die,  the  column  run 
out  being  cut  to  the  desired  m dth  of  pieces.  These  were  air 
dried  and  then  dried  in  a steam-heated  rack  drier. 

2.  Sli'os.  The  slips  used  v/ere  a typical  terra  cotta  slip  and 
a vitreous  white  slip  as  follows: 

(a)  Terra  cotta  slip 
English  China  clay 
Tennessee  Ball  clay  10% 

Feldspar  ^0% 

Flint  2^% 

(b)  Vitreous  white  slip 

Cornwall  stone  ^0% 

English  Ball  clay  1^% 

English  China  clay  20^^ 

Boric  Acid  2% 

Flint  1% 

Calcium  Carbonate  2% 

Barium  Carbonate  2% 

Magnesium  Oxide  1% 

The  nreparation  was  the  same  for  both  slips  and  consisted 
merely  of  grinding  wet  for  three  hours  in  ball  mills  and  lavming 
through  a screen  of  140  meshes  to  the  inch. 


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8 


. Glazes  used.  Two  glazes  were  used,  a fritted  glaze  and  a 
bristol  glaze: 


(a)  Fritted  Glaze: 

Fritt:  - 

Y/hiting  35  uarts 
Feldspar  5^  parts 
Borax  57  parts 
Flint  5'^  parts 
Boracic  acid  1 part 
Ceranic  Formula: 

.3 

.35  cao  .283  AI2  0^ 


.2K2O  .31  B^O^ 

.15  Na20 

(b)  Bristol  Glaze: 


Ceramic  Formula: 


. 27OK2Q 
.234  ZnO 
.396  CaO 
,100  BaO 


• 55  AI2  0^ 


G1  aze  - 
Fritt  160  parts 
White  lead  77  parts 
Feldspar  5^  parts 
China  clay  21  parts 
Flint  44  parts 


3.0  SiO^ 


3-3  Si02 


Batch  weights,  figured  on  the  basis  that  the  coloring 
oxides  renlace  like  amounts  of  CaO. 


Extreme  .005 

150.2  Feldspar 
18,9  Zinc  Oxide 
39*1  Calcium  Carbonate 
19*7  Barium  Carbonate 
51.6  Raw  clay 


iy.9  Calcined  clay 
67.1  Flint 

(.00^  Equivalents  of  coloring  oxide). 
Extreme  .10 

150.2  Feldsnar 
18.9  Zinc  Oxide 
29*6  Calcium  Carbonate 
19.7  Barium  Carbonate 
51.6  Raw  Clay 
17*9  Calcined  Clay 
67.1 F lint 

(.10  equivalent  of  coloring  oxide). 

4.  Biscuited  Tile  Trial  Pieces. 

Trial  pieces  of  biscuited  tile  with  the  anplication  of 
glaze  on  them  were  run  to  assure  a knowledge  of  the  various  col- 
ors developed,  in  case  the  green  oieces  should  not  develop 
pronerly, 

5.  Oxides  used  and  their  source 

(a)  Leukonin  SbOj*  THgO)  Introduced  as  such. 

(b)  Cerium  oxide  (Ce02)  Prepared  by  igniting  basic  ceric 

nitrate  strongly. 

(c)  Ferrous  oxide  (FeO)  Introduced  as  ferric  oxide 

(F620^),  pure. 

( d)  Uranium  oxide  (UpO^)  Introduced  as  sodium  uranate 

^ (Ua2  O5  H^O) 

(e)  Tungstic  acid  (K  WO  ) Introduced  as  such. 

2 4 

(f)  Molybdic  oxide  (MoO^)  Introduced  as  such. 

(g)  Uranium  Ui  trate(U(lI02)  nt  reduce  d as  such. 

(h)  Manganese  dioxide  (MnOp)  Introduced  as  such. 


11 


Blending,  Dipning  and  Firing. 

1.  Blending. 

In  'both  the  fritted  and  the  hri  stol  glaze  the  two  color 
extremes,  .00^  equivalents  and  .10  equivalents  of  color  oxide 
present,  were  prepared  and  the  intermediate  colors  prepared  by 
blending  these  extremes  in  the  oroper  proportions  figured  in 
dry  weight  of  glaze.  All  blending  was  carried  out  on  the  basis 
of  the  weight  of  dry  glaze  oresent  in  the  glaze  mix.  This  was 
found  by  weighing  a certain  known  amount  out  in  a dish,  drying 
the  glaze,  weighing  again  and  calculating  the  weight  of  dry 
material  in  one  gram  of  wet  material  from  the  data  obtained. 

Samnle  Calculation  for  Blending. 

(a)  Determination  of  dry  weight. 

1.  Extreme  .00^  equivalents  coloring  oxide. 

Weight  of  beaker  and  glaze  slip  -147.5 

” ” " and  glaze  slip  dried  141.  Igm. 

” ” ” alone  1 36. Igm. 

Weight  of  slip  147. 5 “^36.1  11.4  gm. 

” ’•  '•  dried  141.1  136. 1 5.O  gm. 

Then  1 gm.  dry  2.28  gm.  wet  glaze  slio. 

2.  Extreme  .10,  calculated  similarly,  gives: 

1 gm.  dry  2.71  wet  glaze  slip. 

3.  The  method  of  blending  i s by  the  position  of 
the  glaze  desired  in  reference  to  the  two  extremes  as  shovm  below. 


O 

0 0 


It  mil  be  noted  that  glaze  .04  for  instance, 
is  seven  (7)  divisions  from  extreme  .005  and  twelve  (12) 


■y  \ 


IliJM 


12 

divisions.  The  calculations  , then,  for  making  up  the  glaze  are 
as  follows: 

50  X 12/19  X 2.28  72.0  gm.  (.005  extreme) 

50  X 7/19  X 2.71  4-9.9  gin*  (.10  extreme) 

2.  Dipping. 

Both  the  si  ins  and  the  glazes  were  dipped.  The  slip  was 
brought  to  a specific  gravity  of  approximately  1.5  as  this  is 
the  most  workable  v/eight  for  dinping.  The  glazes  were  applied 
by  dinning  after  the  slips  v/ere  dinped,  the  specific  gravity 
being  the  same  as  the  slins  when  pieces  were  dipped. 

3.  Biring. 

The  burning  was  all  done  in  one  burn,,  that  is,  the  body, 
slip  and  glaze  were  all  burned,  at  one  lurn^  The  Time  Temperature 
Schedule  for  the  burn  is  shown  in  Graph  ITo.  1.  Care  v/as  exercised 
to  have  an  oxidizing  atmosnhere  in  the  kiln  at  all  times,  and 
ample  time  was  allowed,  at  the  end  of  the  burn  for  the  purpose 
of  ’’soaking”,  or  equalizing  the  temperature  over  the  entire  kiln. 
Cones  four  and  six  v;ere  placed  in  the  saggers  to  indicate  the 
heat  treatment  and  cones  three,  four,  five  and  six  were  used 
as  sight  cones. 

The  burn  went  to  Seger  cone  5* 


9 « 


p.* 


< --^^1 


13 

VI 

Re  suit  s. 

1.  General. 

(a)  The  sight  cone  5 was  well  dov.Ti  and  the  cones  in  the 
saggers  indicated  that  the  cone  ^ heat  treatment  extended  to 
all  narts  of  the  kiln. 

(h)  Fitting  of  glaze,  slip  and  body. 

The  results  of  the  Bloomingdale  Stoneware  nieces  showed 
that  the  method  of  dinning  was  probably  at  fault,  as  the  glazes 
and  slips  rolled  and  beaded  considerably. 

(c)  Biscuited  tile  trials. 

The  glazes  all  developed  well  on  the  biscuited  tile  and 
the  tabulated  results  as  to  color  were  obtained  from  these  trials. 


iriiMiiy 


_ v. 

i'-n 


;j:  ' 

W"' 


, f 


S;'  '-^‘> 


-V,  '.*  -fV  ■■’'>''V-'  T ■'’"■/'•  'I 


tef '‘'v'^  * 


.’«•'•  4 • ^ . 1 *•%•  «^  ‘ * jvi  . ' '4,1 

>^H4a  r ^,  ■•’^T®Kl|L^^^  J 

fete:  ‘ ^ '^vt:  m-  'm*-  ^ 


■'..1 


'd'Y  V-' ( • ‘'‘ .'‘/r''*  T .ybfcj^BwPhaL'-l 

‘ ■ *J.3»  ■ 

StoCT' '*1  Y-  . 


c-~ 

" ■ ■ - 


='«:«  '"■a  *'*'.*-'  ■■  ,T„  fr'' 


liB'  “ ■ ' ■ :" .-  V ;.-:^.^i’;p:^ispwi:  '•/■  * 

H ■«'■<.  r^;  . .,  . ■ 

. S^f, '■  -'■  •■'.'W*  .''.f  j ■' vy;'',.:\*t'-  I'J.J 

I iAJ*  ' '*.HSb.|,  ».  ' '.V  VjdMfflfiffi® 

. - V’  4V!^?v  V. ' ^*  ’ J 


.,•■-*■•!  A'T’Tv  -‘-  ••*  T 

'A. 


--^owifaB 


c ■ ^ 

u '".  < ' '•  u ' * 1 


^ IT:  r ' ' -1 

II  fcv*A‘  . '"  -.I’M 


14 


T bJoI  e ITo . 1 

Equivalents  of  Coloring  Oxide  employed 


Color  Oxide 

.005 

.01 

.02 

.04 

.07 

.10 

1 

U2O3 

Trace 

F51i  ght 

Fai  r 

Good  yellow 

I.'luddy 

Brown 

Almost 
B1  ack 

2 

TiO^ 

Fone 

Fone 

Fone 

Fone 

Fone 

Fone 

3 

2Ka^3b03*7K^0 

Fone 

Fone 

Fone 

Fone 

Trace 

SI  i ght 

4 

C 

Fone 

Fone 

Fone 

Fone 

Trace 

SI  i ght 

PT 

*FeC  (Ba) 

Trace 

Sli  gbt 

SI  i ^-t 

Fair  Light 
Browni sh 

Almo  si 
muddy 

: Muddy 

6 ItFeO  (Mg) 

n 

H 

II 

II 

It 

7 

2FaSbO. . 7KnO 

3 ^ 

Fone 

Fone 

Fone 

Fone 

Fone 

Fone 

8 

U2O3 

T race 

Sli^d^t 

Fai  r 

Good  Yellov.’ 

Mu  ddy 

Almost 
B1  ack 

9 

T102 

Fone 

Fone 

Fone 

Trace 

Tr  ace 

SI  i ght 
Brown  Yel- 
low 

10 

Fe2  O3 

Trace 

Trace 

Sli  ^t 

Pale  BroTO 

Pale 

Brown 

Pale  Gray- 
ish yellow 

11 

Ce02 

Fone 

Fone 

Fone 

Trace 

Cre  am 

Crea.m 

* FeO  in  the  original  Bristol  glaee,  with.  1 equivalent  harium. 

oxide. 

FeO  in  the  original  Bristol  glaze,  except  that  .1  equivalent 
magnesium  oxide  replaces  the  barium  oxide. 

Fos.  1-6  inclusive  Bristol  Glaze. 

Fob.  7 ^ 11  inclusive  Fritted  Glaze. 


/ 


15 

VII 

Conclusi  ons. 

1.  From  the  results  of  the  Blocmingdale  Stoneware  trials  there 
is  obviously  something  v;rong  mth  the  applications  of  the  glaze 
and  slip  on  the  body.  The  writer  has  had  similar  experiences 
7/ith  attemnts  to  dip  Bristol  glazes  on  this  same  body  which  v/ere 
corrected  by  snraying  the  gla^ie  on.  A better  application  could 
no  doubt  have  been  made  by  spraying. 

2.  The  glazes  on  the  tile  trials  were  well  matured,  showing  that 
the  glazes  are  suitable  for  maturity  at  this  temnerature. 

3.  Of  the  two  glazes  the  Bristol  appears  to  have  an  advantage 
over  the  fritted  glaze  for  apnli cation  to  the  green  nieces,  as 
they,  in  general  adhiered  better  on  the  green  nieces  than  the 
fritted  glazes. 

4.  Coloring  Oxides. 

Of  the  coloring  oxides  employed,  only  uranium  and  iron  oxides 
annear  to  be  worth  while  as  a commercially  practicable  coloring 
constituent.  The  higher  members  of  the  Uranium*  series  show  up  gray 
which  is,  no  doubt,  due  to  the  excessive  amounts  used.  Iron 
develons  a fair  ye]low,  but  one  that  is  rather  indistinct  and 
slightly  muddy. 


i6 

Part  Tv;o 

I 

Change?  in  Glaze  Co^n-nosi  ti  on. 

It  appears  that  the  Bristol  glaze  "behaves  "better  than  the 
fritted  glaze  on  green  "bodies  as  the  Bristol  glaze  was  adopted 
as  the  standard. 

The  R.  0.  mem"bers  of  the  glaze  were  varied  some-vdiat  to 
determine  what  effect,  if  any,  this  would  have  on  the  color 
oxides.  The  two  variations  are  as  follows: 

"X”  Bristol 
.333 

.334-  CaO  0.55  Al^  0^  3.3  Sio^ 

.333  YnO 

"Y"  Bristol 

.350  K2O 

.317  CaO  O.55AI2O2  3.3Si02 

.333  YnO 

The  oxides  were  used  to  replace  equiva,lent  amounts  of 
calcium  oxide,  as  in  Part  One. 

Tv;o  other  oxides  v/ere  employed  in  this  hum,  which  were  not 
available  for  use  in  the  first  hum,  namely  tungstic  acid,  and 
molyhdic  oxide.  These  were  used  hoth  alone  and  in  the  presence 
of  .05  equivalents  of  manganese  dioxide. 


17 

II 

Pren  arati  on,  Blending,  Aopli  c ati  on,  Firing. 

1.  The  nrenaration  of  the  glazes  was  the  saire  as  outlined  under 
Part  One. 

2.  Blending  has  already  "been  outlined  in  Part  One,  the  same  method 
being  emnloyed  in  this  burn. 

3.  Application. 

The  method  of  an-^li  cation  was  different  from  that  employed 
in  Part  one.  Instead  of  dipping,  both  the  slip  and  the  glaze  were 
ap-tlied  by  spraying,  which  gave  a good  even  coat,  without  showing 
any  drying  cracks. 

4.  Firing. 

The  firing  schedule  was  the  same  as  that  emnloyed  in  the 
first  burn,  the  si  ^^t  cones  and  the  Seger  cones  being  the  same 
and  the  burn  going  to  the  same  cone--Cone 

The  writer  could  observe  no  indications  of  reducing  conditions 
in  the  kiln.  Care  was  exercised  to  avoid  forcing  the  fires.  The 
cones  indicated  a good  even  cone  5 heat  all  over  the  kiln  with 
the  excention  of  two  saggars  in  the  bottom,  v;hen  it  v/as  estimated 
the  heat  was  cones  three  and  four  re  s'0'=  c tively. 


18 


ill. 

ixesults. 

1.  Application. 

The  application  of  the  glaze  on  the  green  body  was  rather 
thin,  but  it  was  thick  enough  to  indicate  that  the  body,  slip  and 
glaze  were  well  fitted  at  this  cone(Seger  cone  5).  The  majority 
of  the  glazes  indicatea  that  they  would  mature  at  this  cone,  as  is 
shown  in  Table  No. 2. 

2.  Comparison  of  the  slips. 

Of  the  two  slips,  the  vitreous  slip  lends  itself  most  readily 
to  the  proper  maturing  of  body,  slip  and  glaze  at  cone  5. 

3.  Jiiffect  of  absence  of  iiarium  on  the  iron  oxide  yellows. 

A decided  difference  in  the  tone  of  the  iron  oxide  yellows  is 
shown  in  the  absence  of  barium  oxide  from  the  HO  members  of  the 
glaze,  the  ones  without  barium  present  being  much  more  clear  and 
uniform  and  avoiding  the  muddy  appearance  altogether. 


■ ■ T:.  ^ 


t''* 


; '.Nri  b . . .V^-OC. 

. >, u j.  j : . .’ ';  f . ■ ■ 

'•  . V'!:  «Iivi  J4 


■J.i'.  •.•O’t  Ji;nr;M-'C3  5i:  / 


“‘'■/  c).‘ 


\ :■,<■)  «7is'., 

i ''i  j ‘ ' . L ' v; 

\ r. 

r-  *.^  } '">m0;> 

■'  ,w  1."  \l  ■ 

■ ^ ■ 

, ’ :•  o 

' >, .'  .'<  '■  Olfi 

.'.oV  '.'0 

o ■ 

'^y  .ru:  hri 

r -1  4^ 

. ' - ■; 

• ?. 

ixy''!.'  eh  IrC 

■.?:  i.  a ' 

' ■ i' 

•o  - : • 0 .'.:  ■ 

• .■.’i  •<  ,s 

t-r.  ^ 

• : i 

r»  I 


.,  ;0.  j J'l'O'i  L • 

t 

'.'Ol  ■ ■“  .. 


i'. 


Ji:v 


ri  i.xj 

-■il-  'Ij 


I J r.  ^ *■ 

. ^X:  V 

. . ; ,;c‘.--  i;r  SVO*i( 

I ..<-.  S tail:  .0 
, - I,  1.  tj{..  - V 

*-;'■'''  . J‘t\  I ’v . o r " , • w 


, r ,.  • 4\.  - ’ T 

...  , .Ov-.  ...... 

\ r- 

. ..bCltOl  .%  ,'>.; 


19 


Table  ilo.E, 

iJata  on  the  tiaturity  of  the  Glazes • 


Amount  of 


oxide  used 

.005 

.01 

.02 

.04 

,07 

.10 

Bristol: 

^2^3 

0 

X 

X 

X 

0 

0 

ij'egOg 

X 

0 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

MOOg 

X 

X 

X 

X 

X 

X 

”Y”  Bristol: 

°8°3 

X 

X 

0 

0 

X 

0 

X 

X 

0 

0 

0 

0 

X 

X 

X 

X 

X 

X 

UoO, 

0 

0 

0 

0 

X 

0 

Original  Bristol 

LIoO_ 

o 

• 

X 

X 

X 

X 

X 

X 

HgV/0^ 

0 

0 

0 

X 

X 

0 

•'  & MnOg 

X 

X 

X 

X 

X 

X 

MoOg&MnOg 

X 

X 

X 

X 

X 

X 

UaiOgjg  & 
Feldspar 

ji^ritt 

0 

0 

X 

X 

0 

0 

0- 

indie 

a,tes 

glazes 

not  matured 

• 

X- 

indie 

extes 

glazes 

which  matured. 

A* , ' 1*'  ’ *by 


f"'  ■ ^ vji  . toii^  .i''. 


i 


{) 


X 


0 


' ' ,/■ 


. 1.  . 

jiL 

« 

• 

« 

j 

_ 

■'*  ,.  , •■> 

■'  ^ 

,r 

X 

- 

X . 

,'\ 

>v 

■ ' \ ,r  ' \,t-' 

■■  V 

,v  ' . 

vW' 

V 

ip  ■ 

.1 

•\  ■ 

V ' fe-v 

, '"O 

■ , -^j’. 

.':  ' 

S )£ 

. . ' ' ' "'  '1 

• ^ ; “'•  r^; 

5X/^’,;.' 

'•c 

;■"  s 
1 ’ ' 

>;;X' 

■ 

■r'  -‘ 

V 

*- 

'.'■■■  ■ ’v 

:: 

( 

*• 

. V'''--‘'  ■ 

s t 

■ <■'•?'  X 

, .;■> 

X 

’ C- 


. / 

'■  V ' 


o; 


T \ -'  v'.  ■*-'•'*  S' At^*  ^Xl 


Coloring 

Oxide 

.005 

20 

Table  No.  S 
Colors  Obtained 

01  eg.  .02  eg.  .04  eg. 

.07eg. 

.lOeg. 

’’X” 

Bristol 

Trace 

Slight 

Pale 

Muddy 

Cray 

Almost  Black 

FegOg 

Trace 

Trace 

Slight 

Pair 

good 

good  yellow 

H2WO4 

Hone 

None 

None 

None 

buff  tilt-  slightly  buff 
ed 

None  None 

N0O3 

None 

None 

None 

None 

None 

None 

nyit 

Bristol 

Trace 

Slight 

Pale 

Muddy 

Cray 

Almost  Black 

Fe  0 

Trace 

Trace 

Slight 

Pair 

Good  buf 

good  yellow 

H2WO4 

None 

None 

None 

None 

tinted 

yellov; 

None 

slightly  buff 
None 

LloOg 

None 

None 

None 

None 

None 

None 

Original 
Bristol 
Mo  Og 

None 

None 

None 

Trace 

Slight 

Slight  pale  brovm 

H2WO4 

None 

None 

None 

None 

pale 

brown 

None 

None 

H2WO4& 

Light 

Light 

Light 

Light 

Light 

Light  brown 

LtoO£ 

brown 

brown 

brown 

brown 

brown 

MoOc2  8a 

light 

light 

Light 

Light 

Light 

Light  brown 

MnOg 

brown 

brown 

brown 

brown 

brown 

U(U0s)3 

Slight 

Slight 

light 

Pair 

Cood 

Blackish 

V 


. 1 


;> 


ST" 


n 


' . ^ 


✓ 


or 


1 71 

j fiA«  , • 


o 


22 

XV. 

Nummary. 

1.  Uranium  oxide  develops  good  shades  of  lemon  yellow,  except  where 
too  much  is  used,  where  it  turns  black. 

8.  Iron  oxide  develops  good  colors  of  yellow-buff.  The  iron  yellows 
are,  however,  slightly  muddy  in  the  presence  of  barium. 

3,  Tungstic  oxide  and  molybdic  oxide  of  themselves  develop  no  color 
With  .05  equivalents  of  manganese  dioxide  they  develop  light  buff 
browns.  The  manganese,  of  course,  predominates  in  producing  this 
color. 

4.  Ceric  oxide  produces  only  very  faint  yellows,  which  are,  of 
course,  impracticql  for  use  in  terra  cotta  glazes. 

6.  Titanic  oxide,  also,  develops  only  faint  colors,  which  are 
useless. 

6.  Leukonin  as  used  develops  no  color. 

7.  The  application  of  the  glaze  and  slip  by  spraying  leads  to  the 
best  results  as  to  the  fitting  of  the  body,  glaze  and  slip. 


23 


V. 

Conclusions, 

The  Uranium  oxide  color  is  the  best  true  yellow  of  those  used 
here,  Uranyl  nitrate  fritted  with  feldspar  gives  a good  clear 
lemon  yellow,  which  is  very  promising  in  appearance. 

The  and  ”Y”  Bristol  glazes  show  no  improvement  over  the 
original  Bristol  except  in  the  ease  of  iron, which  has  already  been 
noted.  The  one  which,  in  my  opinion,  is  best  for  use  is  the  ”X" 
Bristol,  because  of  its  conformity  to  the  typical  iiristol  HO 
formula  and  because  it  develops  a fine  gloss  and  allows  of  con- 
siderable variation  to  allow  for  fitting  it  to  any  body  on  which 
it  is  used, 

iron  oxide  colors  are  very  good,  especially  v/here  a yellow 
with  a slightly  buff  tinge  is  desired.  The  advantage  of  iron  oxide 
is  its  cheapness  and  availibility  and  comparative  purity  with 
which  it  can  be  obtained. 

The  tungstic  and  molybdic  oxide  glazes  with  manganese  are  not 
true  yellows  at  all.  Their  use  as  such  is  therefore  impossible. 


